hi everyone i had similar problem last month when it was very cold in nyc...i was getting low coolant level message and brought it to dealer..they said it was in fact low and added fluid..they checked for leaks/problems and said they found none..sa said it is common problem in cold weather...i really didnt believe him but didnt have much choice...i forgot to check level when i got car back to see how high plunger was...i checked last week and plunger is at min level...will keep checking...rob